This invention relates generally to low noise sonobuoys and particularly to sonobuoys having a gradient hydrophone completely surrounded by a spherical flow shield which reduces the near field effects of flow and motion noise.
Directional, gradient hydrophones become extremely susceptible to near field effects of flow and motion noise when deployed in a water body. Accordingly, it is desirable to reduce near field noise as much as possible within the immediately surrounding environment and to stablize the motion of the hydrophone within the water body. Prior art hydrophone devices have utilized rigid containers both in spherical and a cylindrical forms to house a hydrophone which is immersed in a liquid. Such devices large enough to keep moving water well away from the hydrophone surfaces are not easily packageable in a conventional sonobuoy canister either because of rigidity or size and often restricted the directional sensitivity of the hydrophone.